Fixed a bug that does not get a space type from index setting when it is empty for compatibility.

CHANGELOG.md

@@ -20,6 +20,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 - Introduced a writing layer in native engines where relies on the writing interface to process IO. (#2241)[https://github.com/opensearch-project/k-NN/pull/2241]
 ### Bug Fixes
 * Fixing the bug when a segment has no vector field present for disk based vector search (#2282)[https://github.com/opensearch-project/k-NN/pull/2282]
+* Fixing it to retrieve space_type from index setting when both method and top level don't have the value. [#2309](https://github.com/opensearch-project/k-NN/pull/2309)
 ### Infrastructure
 * Updated C++ version in JNI from c++11 to c++17 [#2259](https://github.com/opensearch-project/k-NN/pull/2259)
 * Upgrade bytebuddy and objenesis version to match OpenSearch core and, update github ci runner for macos [#2279](https://github.com/opensearch-project/k-NN/pull/2279)

qa/restart-upgrade/src/test/java/org/opensearch/knn/bwc/IndexingIT.java

@@ -154,14 +154,14 @@ public void testKNNIndexBinaryForceMerge() throws Exception {
     }
 
     // Custom Legacy Field Mapping
-    // space_type : "linf", engine : "nmslib", m : 2, ef_construction : 2
+    // space_type : "innerproduct", engine : "nmslib", m : 2, ef_construction : 2
     public void testKNNIndexCustomLegacyFieldMapping() throws Exception {
 
         // When the cluster is in old version, create a KNN index with custom legacy field mapping settings
         // and add documents into that index
         if (isRunningAgainstOldCluster()) {
             Settings.Builder indexMappingSettings = createKNNIndexCustomLegacyFieldMappingIndexSettingsBuilder(
-                SpaceType.LINF,
+                SpaceType.INNER_PRODUCT,
                 KNN_ALGO_PARAM_M_MIN_VALUE,
                 KNN_ALGO_PARAM_EF_CONSTRUCTION_MIN_VALUE
             );

qa/restart-upgrade/src/test/java/org/opensearch/knn/bwc/ScriptScoringIT.java

@@ -64,22 +64,6 @@ public void testKNNL1ScriptScore() throws Exception {
         }
     }
 
-    // KNN script scoring for space_type "linf"
-    public void testKNNLinfScriptScore() throws Exception {
-        if (isRunningAgainstOldCluster()) {
-            createKnnIndex(testIndex, createKNNDefaultScriptScoreSettings(), createKnnIndexMapping(TEST_FIELD, DIMENSIONS));
-            addKNNDocs(testIndex, TEST_FIELD, DIMENSIONS, DOC_ID, NUM_DOCS);
-        } else {
-            QUERY_COUNT = NUM_DOCS;
-            DOC_ID = NUM_DOCS;
-            validateKNNScriptScoreSearch(testIndex, TEST_FIELD, DIMENSIONS, QUERY_COUNT, K, SpaceType.LINF);
-            addKNNDocs(testIndex, TEST_FIELD, DIMENSIONS, DOC_ID, NUM_DOCS);
-            QUERY_COUNT = QUERY_COUNT + NUM_DOCS;
-            validateKNNScriptScoreSearch(testIndex, TEST_FIELD, DIMENSIONS, QUERY_COUNT, K, SpaceType.LINF);
-            deleteKNNIndex(testIndex);
-        }
-    }
-
     // KNN script scoring for space_type "innerproduct"
     public void testKNNInnerProductScriptScore() throws Exception {
         if (isRunningAgainstOldCluster()) {

qa/restart-upgrade/src/test/java/org/opensearch/knn/bwc/WarmupIT.java

@@ -45,14 +45,14 @@ public void testKNNWarmupDefaultLegacyFieldMapping() throws Exception {
     }
 
     // Custom Legacy Field Mapping
-    // space_type : "linf", engine : "nmslib", m : 2, ef_construction : 2
+    // space_type : "innerproduct", engine : "nmslib", m : 2, ef_construction : 2
     public void testKNNWarmupCustomLegacyFieldMapping() throws Exception {
 
         // When the cluster is in old version, create a KNN index with custom legacy field mapping settings
         // and add documents into that index
         if (isRunningAgainstOldCluster()) {
             Settings.Builder indexMappingSettings = createKNNIndexCustomLegacyFieldMappingIndexSettingsBuilder(
-                SpaceType.LINF,
+                SpaceType.INNER_PRODUCT,
                 KNN_ALGO_PARAM_M_MIN_VALUE,
                 KNN_ALGO_PARAM_EF_CONSTRUCTION_MIN_VALUE
             );

src/main/java/org/opensearch/knn/index/engine/SpaceTypeResolver.java

@@ -7,8 +7,10 @@
 
 import org.apache.logging.log4j.util.Strings;
 import org.opensearch.index.mapper.MapperParsingException;
+import org.opensearch.knn.index.KNNSettings;
 import org.opensearch.knn.index.SpaceType;
 import org.opensearch.knn.index.VectorDataType;
+import org.opensearch.common.settings.Settings;
 
 import java.util.Locale;
 
@@ -25,24 +27,30 @@ public final class SpaceTypeResolver {
     private SpaceTypeResolver() {}
 
     /**
-     * Resolves space type from configuration details. It is guaranteed not to return either null or
-     * {@link SpaceType#UNDEFINED}
+     * Resolves space type from configuration details. It is guaranteed not to return null.
+     * When space is not in either method and top level, UNDEFINED will be returned.
+     * This can happen when it is defined at index level which is deprecated and no longer allowed in the future.
+     * In this case, UNDEFINED will be returned.
      *
-     * @param knnMethodContext Method context
-     * @param vectorDataType Vectordatatype
+     * @param knnMethodContext        Method context
      * @param topLevelSpaceTypeString Alternative top-level space type
      * @return {@link SpaceType} for the method
      */
     public SpaceType resolveSpaceType(
         final KNNMethodContext knnMethodContext,
-        final VectorDataType vectorDataType,
-        final String topLevelSpaceTypeString
+        final String topLevelSpaceTypeString,
+        final Settings indexSettings,
+        final VectorDataType vectorDataType
     ) {
         SpaceType methodSpaceType = getSpaceTypeFromMethodContext(knnMethodContext);
         SpaceType topLevelSpaceType = getSpaceTypeFromString(topLevelSpaceTypeString);
 
         if (isSpaceTypeConfigured(methodSpaceType) == false && isSpaceTypeConfigured(topLevelSpaceType) == false) {
-            return getSpaceTypeFromVectorDataType(vectorDataType);
+            final String spaceType = indexSettings.get(KNNSettings.INDEX_KNN_SPACE_TYPE.getKey());
+            if (spaceType == null) {
+                return getDefaultSpaceType(vectorDataType);
+            }
+            return SpaceType.getSpace(spaceType);
         }
 
         if (isSpaceTypeConfigured(methodSpaceType) == false) {
@@ -67,6 +75,13 @@ public SpaceType resolveSpaceType(
         );
     }
 
+    public static SpaceType getDefaultSpaceType(final VectorDataType vectorDataType) {
+        if (vectorDataType == VectorDataType.BINARY) {
+            return SpaceType.DEFAULT_BINARY;
+        }
+        return SpaceType.DEFAULT;
+    }
+
     private SpaceType getSpaceTypeFromMethodContext(final KNNMethodContext knnMethodContext) {
         if (knnMethodContext == null) {
             return SpaceType.UNDEFINED;
@@ -75,13 +90,6 @@ private SpaceType getSpaceTypeFromMethodContext(final KNNMethodContext knnMethod
         return knnMethodContext.getSpaceType();
     }
 
-    private SpaceType getSpaceTypeFromVectorDataType(final VectorDataType vectorDataType) {
-        if (vectorDataType == VectorDataType.BINARY) {
-            return SpaceType.DEFAULT_BINARY;
-        }
-        return SpaceType.DEFAULT;
-    }
-
     private SpaceType getSpaceTypeFromString(final String spaceType) {
         if (Strings.isEmpty(spaceType)) {
             return SpaceType.UNDEFINED;

src/main/java/org/opensearch/knn/index/mapper/KNNVectorFieldMapper.java

@@ -387,13 +387,20 @@ public Mapper.Builder<?> parse(String name, Map<String, Object> node, ParserCont
                 // If the original knnMethodContext is not null, resolve its space type and engine from the rest of the
                 // configuration. This is consistent with the existing behavior for space type in 2.16 where we modify the
                 // parsed value
-                SpaceType resolvedSpaceType = SpaceTypeResolver.INSTANCE.resolveSpaceType(
+                final SpaceType resolvedSpaceType = SpaceTypeResolver.INSTANCE.resolveSpaceType(
                     builder.originalParameters.getKnnMethodContext(),
-                    builder.vectorDataType.get(),
-                    builder.topLevelSpaceType.get()
+                    builder.topLevelSpaceType.get(),
+                    parserContext.getSettings(),
+                    builder.vectorDataType.get()
                 );
+
+                // Set space type to the original knnMethodContext. Since the resolved one can be UNDEFINED,
+                // we must wrap it and pick up the default when it is UNDEFINED.
                 setSpaceType(builder.originalParameters.getKnnMethodContext(), resolvedSpaceType);
                 validateSpaceType(builder);
+
+                // Resolve method component. For the legacy case where space type can be configured at index level,
+                // it first tries to use the given one then tries to get it from index setting when the space type is UNDEFINED.
                 resolveKNNMethodComponents(builder, parserContext, resolvedSpaceType);
                 validateFromKNNMethod(builder);
             }
@@ -484,11 +491,7 @@ private void validateCompressionAndModeNotSet(KNNVectorFieldMapper.Builder build
             }
         }
 
-        private void resolveKNNMethodComponents(
-            KNNVectorFieldMapper.Builder builder,
-            ParserContext parserContext,
-            SpaceType resolvedSpaceType
-        ) {
+        private void resolveKNNMethodComponents(Builder builder, ParserContext parserContext, SpaceType resolvedSpaceType) {
             // Setup the initial configuration that is used to help resolve parameters.
             builder.setKnnMethodConfigContext(
                 KNNMethodConfigContext.builder()

src/main/java/org/opensearch/knn/index/mapper/KNNVectorFieldMapperUtil.java

@@ -146,7 +146,7 @@ static boolean useLuceneKNNVectorsFormat(final Version indexCreatedVersion) {
         return indexCreatedVersion.onOrAfter(Version.V_2_17_0);
     }
 
-    private static SpaceType getSpaceType(final Settings indexSettings) {
+    public static SpaceType getSpaceType(final Settings indexSettings) {
         String spaceType = indexSettings.get(KNNSettings.INDEX_KNN_SPACE_TYPE.getKey());
         if (spaceType == null) {
             spaceType = KNNSettings.INDEX_KNN_DEFAULT_SPACE_TYPE;
@@ -196,15 +196,11 @@ private static int getEfConstruction(Settings indexSettings, Version indexVersio
     static KNNMethodContext createKNNMethodContextFromLegacy(
         Settings indexSettings,
         Version indexCreatedVersion,
-        SpaceType topLevelSpaceType
+        SpaceType resolvedSpaceType
     ) {
-        // If top level spaceType is set then use that spaceType otherwise default to spaceType from index-settings
-        final SpaceType finalSpaceToSet = topLevelSpaceType != SpaceType.UNDEFINED
-            ? topLevelSpaceType
-            : KNNVectorFieldMapperUtil.getSpaceType(indexSettings);
         return new KNNMethodContext(
             KNNEngine.NMSLIB,
-            finalSpaceToSet,
+            resolvedSpaceType,
             new MethodComponentContext(
                 METHOD_HNSW,
                 Map.of(

src/main/java/org/opensearch/knn/plugin/rest/RestTrainModelHandler.java

@@ -151,6 +151,11 @@ && ensureSpaceTypeNotSet(topLevelSpaceType)) {
             vectorDataType = VectorDataType.DEFAULT;
         }
 
+        if ((knnMethodContext == null || knnMethodContext.getSpaceType() == SpaceType.UNDEFINED)
+            && topLevelSpaceType == SpaceType.UNDEFINED) {
+            topLevelSpaceType = SpaceTypeResolver.getDefaultSpaceType(vectorDataType);
+        }
+
         ensureIfSetThenEquals(
             MODE_PARAMETER,
             mode,
@@ -163,8 +168,9 @@ && ensureSpaceTypeNotSet(topLevelSpaceType)) {
         );
         SpaceType resolvedSpaceType = SpaceTypeResolver.INSTANCE.resolveSpaceType(
             knnMethodContext,
-            vectorDataType,
-            topLevelSpaceType.getValue()
+            topLevelSpaceType.getValue(),
+            null,
+            vectorDataType
         );
         setSpaceType(knnMethodContext, resolvedSpaceType);
         TrainingModelRequest trainingModelRequest = new TrainingModelRequest(

src/test/java/org/opensearch/knn/index/KNNESSettingsTestIT.java

@@ -5,20 +5,31 @@
 
 package org.opensearch.knn.index;
 
-import org.opensearch.knn.KNNRestTestCase;
-import org.opensearch.knn.index.query.KNNQueryBuilder;
-import org.opensearch.knn.plugin.stats.StatNames;
+import org.apache.hc.core5.http.ParseException;
 import org.apache.hc.core5.http.io.entity.EntityUtils;
 import org.opensearch.client.Response;
 import org.opensearch.client.ResponseException;
 import org.opensearch.common.settings.Settings;
+import org.opensearch.common.xcontent.XContentFactory;
 import org.opensearch.core.rest.RestStatus;
+import org.opensearch.knn.KNNRestTestCase;
+import org.opensearch.knn.KNNResult;
+import org.opensearch.knn.index.query.KNNQueryBuilder;
+import org.opensearch.knn.plugin.stats.StatNames;
 
 import java.io.IOException;
+import java.util.Arrays;
 import java.util.Collections;
+import java.util.HashSet;
+import java.util.List;
 import java.util.Map;
+import java.util.Set;
 
 import static org.hamcrest.Matchers.containsString;
+import static org.opensearch.knn.TestUtils.KNN_VECTOR;
+import static org.opensearch.knn.TestUtils.PROPERTIES;
+import static org.opensearch.knn.TestUtils.VECTOR_TYPE;
+import static org.opensearch.knn.common.KNNConstants.DIMENSION;
 
 public class KNNESSettingsTestIT extends KNNRestTestCase {
 
@@ -149,4 +160,59 @@ public void testCacheRebuiltAfterUpdateIndexSettings() throws Exception {
 
         assertEquals(0, indicesInCache.size());
     }
+
+    public void testKNNLegacySpaceTypeIndexingTest() throws IOException, ParseException {
+        // Configure space_type at index level. This is deprecated and will be removed in the future.
+        final Settings indexSettings = Settings.builder()
+            .put("index.knn", true)
+            .put("knn.algo_param.ef_search", 100)
+            .put("knn.space_type", SpaceType.INNER_PRODUCT.getValue())
+            .build();
+
+        // This mapping does not have method.
+        final String testField = "knn_field";
+        final String testIndex = "knn_index";
+        final String mapping = XContentFactory.jsonBuilder()
+            .startObject()
+            .startObject(PROPERTIES)
+            .startObject(testField)
+            .field(VECTOR_TYPE, KNN_VECTOR)
+            .field(DIMENSION, 2)
+            .endObject()
+            .endObject()
+            .endObject()
+            .toString();
+
+        createKnnIndex(testIndex, indexSettings, mapping);
+
+        // Ingest data.
+        float[] queryVector = new float[] { 2, 3 };
+        final int k = 2;
+
+        float[][] vectorData = new float[5][2];
+        vectorData[0] = new float[] { 11.7f, 2.7f };  // distance=31.5
+        vectorData[1] = new float[] { 20.9f, 3.9f };  // distance=53.5 <- answer
+        vectorData[2] = new float[] { 3.77f, 4.22f }; // distance=20.2
+        vectorData[3] = new float[] { 15, 6 };        // distance=48 <- answer
+        vectorData[4] = new float[] { 4.7f, 5.9f };   // distance=27.1
+
+        bulkAddKnnDocs(testIndex, testField, vectorData, vectorData.length);
+        flushIndex(testIndex);
+
+        // Send a query and verify scores are correct.
+        Response searchResponse = searchKNNIndex(
+            testIndex,
+            KNNQueryBuilder.builder().k(k).fieldName(testField).vector(queryVector).build(),
+            k
+        );
+
+        List<KNNResult> results = parseSearchResponse(EntityUtils.toString(searchResponse.getEntity()), testField);
+
+        assertEquals(k, results.size());
+        Set<String> docIds = new HashSet<>();
+        for (KNNResult result : results) {
+            docIds.add(result.getDocId());
+        }
+        assertEquals(new HashSet<>(Arrays.asList("1", "3")), docIds);
+    }
 }

src/test/java/org/opensearch/knn/index/OpenSearchIT.java

@@ -325,6 +325,7 @@ public void testVectorMappingValidation_invalidDimension() {
                 createKnnIndexMapping(FIELD_NAME, KNNEngine.getMaxDimensionByEngine(KNNEngine.DEFAULT) + 1)
             )
         );
+
         assertThat(
             ex.getMessage(),
             containsString(